Nonh-Holland PHYSICS LETTERS A Quantum Zeno effect with the Feynman-Mensky path-integral approach

A model for the quantum Zeno effect based upon an effective Schriidinger equation originated by the path-integral approach is developed and applied to a two-level system simultaneously stimulated by a resonant perturbation. It is shown that inhibition of stimulated transitions between the two levels appears as a consequence of the influence of the meter whenever measurements of energy, either continuous or pulsed, arc performed at quantum level of sensitivity. The generality of this approach allows one to qualitatively understand the inhibition of spontaneous transitions as the decay of unstable particles, originally presented as a paradox of the quantum measurement theory. The quantum measurement theory has been developed in the thirties to understand the problems which arise when quantum mechanical formalism is interpreted and confronted with its macroscopic limit. Some of the debates originated by the matching between quantum and classical worlds assumed the form of paradoxes and have been discussed in terms of ideal experiments. This is the case of the so-called quantum Zeno effect [I-S], i.e., the inhibition of the free evolution of a system subjected to continuous measurements. In the original example of Misra and Sudarshan an unstable particle whose trajectory is continuously monitored should never be observed to decay. Due to recent technological progress in the measurement of physical quantities, especially to quantum optics, in the physics of superconducting coherent devices such as SQUIDs, and in experimental gravitation, some of these ideal experiments can be actually performed [6]. Claims of the observation of th